Market adoption of wireless LAN (WLAN) technology has exploded, as users from a wide range of backgrounds and vertical industries have brought this technology into their homes, offices, and increasingly into the public air space. This inflection point has highlighted not only the limitations of earlier-generation systems, but also the changing role that WLAN technology now plays in people's work and lifestyles across the globe. Indeed, WLANs are rapidly changing from convenience networks to business-critical networks. Increasingly users are depending on WLANs to improve the timeliness and productivity of their communications and applications, and in doing so, require greater visibility, security, management, and performance from their networks.
In Voice over Internet Protocol (VoIP) systems and, in particular, VoIP over WLAN systems there are many points in the network that can cause audio and quality of service impairments to the end users. For example, congestion or interference associated with the WLAN, or congestion on a WAN connection, may degrade network through-put and hence VoIP performance. Also, there may be networking equipment or wireless clients that are misconfigured or have latent bugs which impair the quality of service provided to real time protocol streams. There may be coverage holes in areas of the network. For VoIP over WLAN calls, there is the added complexity which arises from user mobility. Since users may often roam between several wireless access points during the course of a call, a quality of service issue may arise when a wireless client roams from one wireless access point to another. Also, poor quality of service may be caused by interference (e.g., a microwave oven) that is near only one of the wireless access points used during a call. In this situation, a network administrator, when attempting to diagnose the problem, may not recognize that the quality of service (QoS) issue only happens in certain areas of the building. Furthermore, that the problem appears to the end-user as intermittent may render it difficult for a network administrator to determine the root cause of an end-user's complaint, such as if the root cause is associated with the wireless client or with the VoIP network.